In Asymptomatic Severe Aortic Stenosis, Is Earlier Intervention Better?

Kenny Lin, MD, MPH
Posted on November 25, 2024

Affecting three in 100 adults older than 65 years, aortic stenosis is classified as mild, moderate, and severe based on echocardiographic measurements. The onset of symptoms—dyspnea, volume overload, angina, syncope—is associated with a poor prognosis and is the usual indication for aortic valve replacement. Although valve replacement traditionally required open surgery, transcatheter aortic valve implantation (TAVI) has become increasingly common. A current JAMA review article quotes a 2020 American College of Cardiology/American Heart Association guideline as recommending surgical aortic valve replacement (SAVR) for patients younger than 65 years, TAVI for patients 80 years or older, and either procedure in patients 65 to 79 years, depending on operative risk and comorbidities.

A recent editorial in the Journal of the American Heart Association discussed a “paradigm shift” in management of severe aortic stenosis: 69% of Medicare fee-for-service beneficiaries who underwent aortic valve replacement from 2012-2019 had TAVI, with the percentage undergoing SAVR falling from 75% in 2012 to just 10% in 2019. In addition, the overall volume of procedures tripled during this period, suggesting either a dramatic increase in disease severity or more likely, a lower threshold for intervention.

Whether aortic valve replacement in older adults without symptoms of severe aortic stenosis is more beneficial than waiting for symptoms of left ventricular dysfunction to develop is a topic of ongoing research. Two randomized trials published last month shed some light on this question. In a multicenter trial in the United States and Canada, 901 patients older than 65 years (mean age 75.8 years) with asymptomatic severe aortic stenosis were randomized to early TAVI or guideline-recommended clinical surveillance. The primary endpoint was a composite of death, stroke, or unplanned cardiovascular hospitalization. After a median follow-up of 3.8 years, patients assigned to early TAVI had lower mortality (8.4% vs 9.2%), fewer strokes (4.2% vs 6.7%), and fewer unplanned hospitalizations (20.9% vs 41.7%). Of the clinical surveillance group, 87% eventually underwent aortic valve replacement.

A second trial in the United Kingdom and Australia studied 224 patients (mean age 73 years) with asymptomatic severe aortic stenosis and a cardiac MRI showing myocardial fibrosis, which predicts left ventricular decompensation and a poor long-term outcome. Participants were randomized to early aortic valve replacement or conservative management. Although the primary outcome, a composite of all-cause death and unplanned hospitalization related to aortic stenosis, occurred less frequently in the intervention group (18%) than in the control group (23%), this difference was not statistically significant (hazard ratio = 0.79; 95% CI, 0.44-1.43). An accompanying editorial observed that this trial, which fell short of its target enrollment of 356 patients, was underpowered to detect a difference in the outcome. Further, because of scheduling difficulties, 14% of participants in the intervention group had not received valve replacement at 12 months after enrollment. Finally, based on older guidelines that limited TAVI to patients at high operative risk, 75% of the intervention group had SAVR rather than TAVI.

Although the results of these trials can be interpreted as favoring early TAVI in patients with asymptomatic severe aortic stenosis, more studies are needed to ensure that the “paradigm shift” toward early intervention is based on good evidence rather than surgical preference.